[RFI] Bosch Heat Pump

[Jim Brown]

Hi Wes,

No experience to share, but I can share what I've learned about these 
systems in general from those who have experience with variable speed 
systems.

A common problem is caused by layout of the installation, where the 
controller is widely displaced from the motor, poor wiring practices are 
followed, creating both magnetic and EM fields. My first detailed info 
was from the late Neil Muncy, W3WJE, who as a consultant encountered 
strong magnetic fields from controllers for a large bank of elevator 
motors in at the NJ Performing Arts Center, for which he had designed 
sound systems. The trash was coupling into mic lines via Pin One 
Problems and a cable defect called Shield-Current-Induced Noise. Details 
of the latter mechanism in an AES Paper on my website. In the process of 
diagnosing and solving the problem, he found internal applications notes 
from a mfr of those control systems.

Solutions include twisted pair for all current-carrying conductors, and 
including bonding conductors that intimately follow the current carrying 
conductors, thus minimizing both the magnetic field and loops sufficient 
to act as antennas. One of the loops is formed bypass capacitors to 
building and/or frame ground; DC and mains fundamental follows the path 
of least resistance, while higher frequencies follow the path of least 
impedance; running that bonding conductor with the power forms a 
transmission line, providing that lower impedance. I learned this 
fundamental principle at an IEEE Engineering Conference many years ago.

An EE consultant I met nearly 20 years ago who was the father of my 
client contact at a church got to chatting about this problem, and we 
found ourselves nodding our heads in sync as to solutions.

In summary, it's related both to design/construction of the hardware and 
to how systems are installed.

Another thing I learned as a result of long experience in the EMC 
Working Group of the AES Standards Committee is that Europe pays a lot 
more attention to EMC than we do, with the result that some products 
designed and built there to sell there, and exported here, tend to be 
better than average EMC performers. I experienced that with HF radio in 
a Volvo S80 that had no problems, as opposed to my Toyota Sequoia (big 
SUV), whose computer went into "limp home" along I-80 in Northern NV. 
Luckily I had tools that allowed me to reboot it by disconnecting the 
battery.

73, Jim K9YC


On 6/26/2022 3:19 PM, Wes Stewart via RFI wrote:
> I'm considering replacing my 15 year old Trane dual compressor, variable speed blower roof top packaged heat pump.  The ECM blower motor generates a little hash that I can hear on 10-meters with the beam pointed at the house, 100 feet away but it's not serious.
> I'm considering a Bosch Inverter heat pump which gets rave reviews for being efficient and quiet but but I'm not sure it would be electrically quiet.